Adsorption Behavior Of Glucose And Gluconic Acid On Pyrite And Arsenopyrite During Biological Oxidation

Bacteria adsorption on mineral surface is one of the key steps in biological oxidation,The bacteria adsorbed on the mineral surface using the exopolysaccharides(EPS)layer.In this paper,the adsorption behavior of two key substances in EPS layer,(glucose and gluconic acid),on the surface of main gold-bearing minerals(pyrite and arsenopyrite)were studied.It provides a theoretical basis for studying the adsorption of EPS on the mineral surface and the adsorption of bacteria on the mineral surface.In this paper,the adsorption behavior of the four adsorption combinations is studied by Density Functional Theory calculations,molecular dynamics calculations,adsorption experiments and electrochemical experiments.Density Functional Theory calculations show that:In pyrite,arsenopyrite surface,when glucose and gluconic acid adsorbed on pyrite and arsenopyrite crystals,some electrons are transferred from pyrite and arsenopyrite crystals to glucose and gluconic acid molecules.Glucose is adsorbed on the surface of pyrite and arsenopyrite by aldehyde end and gluconic acid is adsorbed on pyrite and arsenopyrite by carboxy end.The eletron transfor ability order of pyrite/glucose,arsenopyrite/glucose,pyrite/gluconic acid,arsenopyrite/gluconic acid is pyrite/glucose>arsenopyrite/glucose>pyrite/gluconic acid>arsenopyrite/gluconic acid.Molecular dynamics calculations show that:when glucose,gluconic acid adsorbed on the pyrite surface,the adsorption configuration was a 'sandwich' structure,sandwich middle layer were water molecules and gluconic acid molecules,respectively;Glucose,gluconic acid adsorbrd on the arsenic surface instability with desorption trend.The adsorption isotherms showed that the adsorption structure of pyrite/glucose was bilayer adsorption,while the adsorption of arsenopyrite/glucose,pyrite/gluconic acid and arsenopyrite/gluconic acid was monolayer adsorption.The adsorption configurations of the four adsorption combinations obtained by the experiment are meet agreement with those obtained by the molecular dynamics,saturated adsorption capacity are meet agreement with electron transfer ability,the order of saturated surface coverage of the four adsorption combinations was pyrite/gluconic acid>arsenopyrite/glucose>pyrite/glucose>arsenopyrite/gluconic acid.